Automatic positioning device

ABSTRACT

A method and apparatus for rapidly positioning a movable device longitudinally inside a tubular structure, such as a pipe, wherein a sensing means attached to said movable device functions to position said movable device responsive to a changing magnetic field generated by an establishing means positioned at a preselected location exterior to said pipe. When said movable device is required to be sequentially positioned longitudinally at a series of locations in one direction inside said pipe, the method and apparatus automatically re-positions said movable device at each location in the desired sequence. This abstract is neither intended to define the invention of the application which, of course, is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way.

Clavin et a1.

Dec. 12, 1972 AUTOMATIC POSITIONING DEVICE Inventors: Edward A. Clavin,Houston; Donald H. McCullough, Cypress; David R. McCullough, Houston,all of Tex.

Crc-Crose Houston, Tex.

Filed: March 31, 1971 Appl. No.: 129,702

Assignee: International, Inc.,

US. Cl. ..72/2l, 72/380, 72/466 Int. Cl ..B2ld 9/00, B2ld 11/22 Field ofSearch ..72/369, 380, 398, 430, 465, 72/466, 21; 254/1345; 340/21, 196;324/34; 191/2; 180/98 References Cited UNITED STATES PATENTS PrimaryExaminer- Lowell A. Larson Attorney-J. Vincent Martin, Joe E. Edwardsand Jack R. Springgate [S 7 ABSTRACT A method and apparatus for rapidlypositioning a movable device longitudinally inside a tubular structure,such as a pipe, wherein a sensing means attached to said movable devicefunctions to position said movable device responsive to a changingmagnetic field generated by an establishing means positioned at apreselected location exterior to said pipe. When said movable device isrequired to be sequentially positioned longitudinally at a series oflocations in one direction inside said pipe, the method and apparatusautomatically re-positions said movable device at each location in thedesired sequence. This abstract is neither intended to define theinvention of the application which, of course, is measured by theclaims, nor is it intended to be limiting as to the scope of theinvention in any way.

20 Claims, 17 Drawing Figures P'A'TENTED DEC 12 I972 SH'EET 1 BF 5EDWARD A CLAVlN DONALD H. MFCuLLoueH DAVID R. MPCULLOUGH INVENTORSynuzjnaj BY M ATTORNEYS PAIENTEMEB 12 I972 3. 705, 506

SHEET 2 BF 5 fl I88 F I84 k 202 l V FWD I 2* I i 1 I76 ON i OFF I i a aL l T L l fl REV l T REV r-EM!TTER DRIVER MEANS I64 EMITTER AUTO i con sI a? T j F 5 Z ACTUATOR MEANS EDWARD A. CLAVIN DONALD H. M9CuLLoueHDAVID R. MFCULLOUGH INVENTORS 9 Wavy/M04 ATTORNEYS PITENTEMEMII?!3.705506 SHEET S (if 5 p EDWARD A. CLAVIN DONALD H. M.CCULLOUGH DAVID R.MFCULLOUGH INVENTORS. VWMWA 7 147 ll 6 BY ATTOR AUTOMATIC POSITIONINGDEVICE BACKGROUND OF THE INVENTION In the construction, bending andinstallation of pipe, a plurality of types of movable devices (usuallyselfpropelled) are often employed to accomplish desired functions. Suchmovable devices are generally required to move longitudinally inside thepipe and stop at a desired location to perform a desired function.

One such movable device is the pipe supporting mandrel for pipe bendingmachines disclosed in US. Pat. No. 3,109,477. Such mandrel isconstructed so that it may easily move longitudinally within the pipe toa desired location and, having reached such location, may be expandedagainst the interior surface of the pipe to support the pipe during thebending operation. Once the bending operation at that location iscomplete, the mandrel may be contracted and moved longitudinally to thenext desired location.

At the present time the most common apparatus for positioning movabledevices, such as the pipe supporting mandrel, longitudinally inside apipe involves manual controls extending out the end of the pipe and, assuch, is both difficult to handle and time consuming.

SUMMARY OF THE INVENTION The present invention relates to an improvedmethod and apparatus of positioning a movable device at a desiredlocation along one side of a partition with respect to an elementlocated on the other side of said partition. Additionally, the presentinvention has application to a process in which it is desired that saidmovable device be positioned at a series of desired locations in onedirection along the partition.

The apparatus of the present invention employs an electromagnetic meansattached in a desired fixed relationship to an element on one side ofthe partition. Such electromagnetic means establishes a periodicallychanging magnetic field and is positioned in a close spaced relationshipto the partition so that said partition is within said changing magneticfield. A sensing means employing the phenomenon of electromagneticinduction is attached in a desired fixed relationship to the movabledevice on the other side of the partition. Said sensing means generatesan electromagnetic voltage signal responsive to the changing magneticfield it senses, which electrical signal functions to position saidestablishing means and said sensing and generating means andconsequently said movable device and said element in a desiredrelationship with each other.

More specifically, the present invention has particular application toand is herein described with reference to the positioning of a pipesupporting mandrel longitudinally inside a pipe with respect to anexternal pipe bending machine. During the pipe bending process theapparatus of the present invention automatically positions the mandrelat a series of longitudinal locations in one direction inside the pipeas the pipe is moved in the pipe bending machine to successive locationsfor successive bends.

It is an object, therefore, of this invention to provide an improvedmethod and apparatus for positioning elements on opposite sides of apartition in a desired relationship to each other.

It is an additional object of this invention to provide an improvedmethod and apparatus for the positioning of a movable devicelongitudinally inside a pipe.

Another object is an improved method and apparatus for the positioningof a movable device longitudinally inside a pipe in which thepositioning of said movable device is accomplished without employing anymeasurements inside the pipe.

Still another object is when a movable device is to perform functions ata plurality of sequential locations in one direction longitudinallyalong the inside of the pipe, the method and apparatus willautomatically reposition such movable device at such locations.

Still another object of this invention is to provide an improved methodand apparatus for the positioning of a movable device longitudinallyinside a pipe in which a sensing means, attached to the movable devicemoving longitudinally inside the pipe, will detect a changing magneticfield generated by an establishing means positioned exterior to thepipe, and will function responsive to said field to positionlongitudinally said device.

A still further object is to provide an improved pipe supporting mandrelwhich will automatically position and set itself to support the pipeeach time the pipe is moved in one direction for a subsequent bend,which position of the mandrel is the desired internal support positionfor bending with respect to the external bending machine.

BRIEF DESCRIPTION OF THE DRAWINGS The invention itself both as toorganization and method of operation, as well as additional objects andadvantages, is more fully explained in the following description whenread in connection with the accompanying drawings in which:

FIG. 1 is a side view of an improved pipe supporting mandrel of thepresent invention in its contracted position within a pipe shown insection positioned in a schematically illustrated pipe bending machine.

FIG. 2 is an end view of a mandrel taken on line 2-2 in FIG. 1.

FIG. 3 is a side view of a removably secured guide means supporting thehose to the improved mandrel of the present invention.

FIG. 4 is a view of such removably secured guide means taken on line 4-4in FIG. 3.

FIG. 5 is a sectional view of a pipe showing the sensing means andestablishing means of the present invention in contact therewith, andshowing the general arrangement of the mechanical portions thereof.

FIG. 6 is a view of the sensing means taken on line 6-6 of FIG. 6.

FIG. 7 is a view of the establishing means taken on line 7-7 of FIG. 5.

FIG. 8 is a block diagram of the electrical and related components ofthis invention.

FIG. 9 is a schematic diagram of the electrical components locatedexterior to the pipe.

FIG. 10 is a schematic diagram of the electrical components located onthe mandrel.

FIGS. 1 1(A) through 1 1(0) are a series of schematic side views ofcertain parts of a pipe bending machine, a pipe, and an improved mandrelaccording to this invention, illustrating the operation of the improvedmandrel in conjunction with a pipe bending machine.

l060l0 (X177 DESCRIPTION OF THE PREFERRED EMBODIMENT: GENERALLY FIG. 1is a side view of a pipe supporting mandrel, such as is disclosed in US.Pat. No. 3,109,477, showing it in a contracted position within afragment of a pipe 20, such pipe in turn being illustrated schematicallywithin certain parts of a pipe bending machine. The pipe bendingmachine, broadly designated by the numeral 22, is a conventionalapparatus provided with a transversely arcuate support 24 for the pipe20 together with a transversly concave but longitudinally convex bendingdie 26 in diametrically opposed relationship to the support 24. The pipe20 is positioned longitudinally in the pipe bending machine by ordinarymeans; proper positioning of the pipe 20 is not difficult because theexterior of such pipe is visible with respect to the components of thebending machine.

The pipe supporting mandrel, broadly designated by the numeral 28, is inthe nature of an elongated flexible body 30 provided with spiderlikeframework 32 and 34 at its ends. In the following explanation, the endof the mandrel having the framework 32 is the forward end of the mandreland the end of the mandrel having the framework 34 is the *rear" end ofthe mandrel (longitudinal movement of the mandrel toward the forward endis referred to as the forward direction and longitudinal movement towardthe rear end is referred to as the reverse" direction). Body 30 includesthree identical longitudinally spaced expansion units or assemblies 36,38 and 40. The details of such expansion units are not shown, but eachsuch unit is constructed of ordinary means and functions to expandpneumatically by compressed air a plurality of radially reciprocalplungers (not shown). Expansion actuator means 42 (shown schematicallyin FIG. a standard device such as a fluid piston, functions pursuant toan electri cal signal to pass and interrupt the flow of compressed airto the expansion units 36, 38 and 40. The plungers function to expandand hold the shoes 44 and the extending flexible strips 46 in firmengagement with the interior wall of the pipe 20, thereby providingsupport for the pipe during the bending process.

Attached to the framework 34 of the mandrel is a container 48 in whichare located certain of the electrical components and a DC battery 50 topower such electrical components.

Forward and reverse movement of the mandrel is provided by a drive ofordinary means. US. Pat. No. 3,109,477 describes in detail theconstruction of such a drive means, including a fluid driven primemover. The mandrel 28 described herein utilizes such a fluid drivenprime mover 52 which is attached to the framework 32 and which operateson compressed air. Also attached to the framework 32 is theforward/reverse actuator means 54 which functions to control the flow ofthe compressed air to the fluid driven prime mover 52 to drive suchprime mover in either the forward or reverse direction and to shut offthe flow to stop the prime mover.

The operations of the prime mover 52, on the one hand, and the expansionunits 36, 38 and 40, on the other, are mutually exclusive; therefore,the same source of compressed air can easily be used for both. Thecompressed air is supplied to the expansion units and prime mover of themandrel through a hose 56 which extends through a removably securedguide means 58 to a spring loaded revolving storage wheel 59 and sourceof compressed air located exteriorally of the pipe 20 remote from themandrel.

The revolving storage wheel 59 is shown schematically above the bendingdie 26 in close proximity to the bending machine 22. Such locationallows easy access to the wheel by the operator of the bending machineand removes the wheel from the longitudinal path of the mandrel whileoutside the pipe. However, since the mandrels prime mover preferably hascompressed air supplied to it both while inside and outside of the pipe,the guide means 58 ensures that the hose 56 has free passage at alltimes from the storage wheel 59 to the mandrel. Such guide means 58 isattached to the end of the pipe (as shown in FIG. I) when the mandrel isin the pipe and attached to the mandrel itself when such mandrel isoutside the pipe.

A means to establish a periodically changing magnetic field of desiredfrequency and magnetic intensity is placed in close spaced relationshipto the exterior surface of the wall of the pipe at a desiredrelationship with respect to the pipe bending machine to generate amagnetic field which will flow into the wall of the pipe. In thepreferred embodiment of this invention, such establishing means 60(where shown) includes at least one electromagnet comprised of aU-shaped core of ferromagnetic material, such as cold rolled steel,around which is coiled a conductor capable of carrying electric current.The magnetic field is created when electric current is driven throughsuch coiled conductOl'.

If the material comprising the wall of the pipe has a permeability ofmagnetism approximately equal to that of free space (such as a plasticpipe), then the magnetic flux of the field will extend relativelyundisturbed through such wall into the free space interior of the pipe.If, however, the permeability of magnetism of the wall of the pipe ismuch greater than that of free space (such as a ferromagnetic. metallicpipe), the effect of the magnetic flux generated by the electromagnet isto align the spinning electrons in such wall so that they themselvesbecome sources of magnetic flux and the original flux distribution isdisrupted. Most of the magnetic lines emanating from the positive poleof the electromagnet are then passed into the metallic wall of the pipe,travel through such wall to a location therein adjacent to the negativepole of the electromagnet, and pass back to the negative pole of theelectromagnet. The pipe wall acts as a shield with respect to theinterior free space region of the pipe. It has been found, however, thateven when the pipe wall has a high permeability of magnetism, theparameters to be discussed below can be varied so that some portion ofthe magnetic flux emitted by the electromagnet passes through the wallof the pipe and travels through the free space interior of the pipeprior to being drawn back through the wall of the pipe to the negativepole of the electromagnet.

Certain parameters, some of which may be controlled by the operator ofthe bending machine, afiect the amount of magnetic flux which will passinto the free space interior of the pipe. The permeability of magnetismof the wall of the pipe is of course a principal parameter, but onewhich cannot be controlled by the operator. However, the operator cancontrol the magnetic intensity of the magnetic field being establishedand, therefore, affect the ability of the magnetic flux to penetrate thewall of the pipe. The spaced relationship between the poles of theelectromagnet and the exterior surface of the pipe is another easilyvaried parameter. If the poles are in direct contact with the wall ofthe pipe, the pipe acts as a keeper" and almost all of the magnetic fluxflows through the pipe from the positive to the negative terminal of theelectromagnet. On the other hand, as the poles are moved away from theexterior surface of the pipe, the free space region causes thereluctance to increase dramatically. And at some point the magnitude ofthe reluctance will be such that the magnetic field will not supplysufi'icient magnetic flux to the pipe to penetrate into the interiorfree space region.

If a longer vertical magnetic field is desired on the interior of thepipe, a plurality of electromagnets may be utilized in the establishingmeans. Since a pipe supporting mandrel may on occasion walk up one orthe other of the interior walls of the pipe, the preferred embodiment ofthis invention utilizes two identical U- shaped electromagnets. EachU-shaped electromagnet is mounted so that its ends are verticallyaligned, and the two electromagnets themselves are vertically alignedwith respect to each other. The positive pole of the first electromagnetis placed adjacent to but in spaced relationship with the negative poleof the second electromagnet. The spaced distance between such positiveand negative poles now becomes an additional parameter which may bevaried by the operator to affect the amount of magnetic flux penetratingthe pipe wall.

A means to sense the periodically changing magnetic field emitted by theestablishing means and existing in the free-space interior of the pipeis mounted on the mandrel at a desired location. In the preferredembodiment of this invention, such sensing means 62 is comprised of aconductor capable of carrying electric current coiled around aferromagnetic core. Such coiled conductor and core are attached to themovable mandrel 28 in close spaced relationship with the interiorsurface of the pipe 20. As such coil and core move into the magneticfield generated by the establishing means, the change in flux throughsuch coil generates an electric current through the conductor and causesa difference of voltage potential between its ends.

It has been found that the coiled conductor on the core does not haveinduced therein a sufficient voltage potential simply by being movedlongitudinally through a magnetic field generated by a direct currentflowing through the establishing electromagnet. And upon cessation ofrelative movement between the conductor and the electromagnet, novoltage potential is induced. Therefore, an alternating current (ratherthan a direct current) is preferably driven through the establishingelectromagnet to increase the rate of change of magnetic flux at everypoint in the magnetic field. In the preferred embodiment of theestablishing means a sixty cycle per second square-wave alternatingcurrent signal is driven through the coiled conductor in theelectromagnets.

Experimentation has revealed that the frequency of the current signaldriven through the electromagnets has a marked effect on the accuracy ofthe sensing var-1 means. The higher the frequency of the alternatingcurrent, the greater the propensity of the magnetic field to propagate.An alternating current with a frequency of say 10,000 cycles per secondgenerates a magnetic field which flows through the walls of the pipealong the entire length of the pipe; the pipe acts as an antenna and thesensing means will detect changing magnetic fluxes at every point insidethe pipe. As the frequency of the alternating current is reduced, therange of the magnetic field decreases. In the preferred embodiment ofthe establishing means according to this invention, the 60 cycles persecond signal generates a magnetic field which penetrates the wall onlya few inches longitudinally along the pipeline in either direction fromthe electromagnets. Even with this low frequency, however, there will bemagnetic fluxes emanating from both ends of a ferromagnetic pipe due tothe pipe itself tending to act as a magnet. But these magnetic fluxes donot adversely affect the accuracy of the sensing means inside the pipeso long as such sensing means is more than a few inches away from theends of the pipe.

To utilize properly the pipe supporting mandrel 28 in the pipe bendingprocess, it is preferred that for each bend of the pipe the verticalcenterline of the mandrel be approximately coincidental with a traversevertical plane through the bending die 26 of the pipe bending machinerepresentative of the center of that portion of the die which impartsbend to the pipe. This is because the segment of the pipe which is to bebent and which is to be supported is aligned with said traverse verticalplane of the bending die.

In the preferred embodiment, establishing means 60 is mountedexteriorally of the pipe 20 so that the vertical centerline 64 (FIGS. 7and 11) of its vertically aligned U-shaped electromagnets is a knowndistance X longitudinally from the desired traverse vertical plane 66(FIG. 11) of the bending die 26. Sensing means 62 is mounted on themandrel 28 so that the vertical centerline 68 (FIGS. 1 and 8) of itssensing coil is located longitudinally the same distance X from thevertical centerline 70 (FIG. 1) of the mandrel 28. Sensing means 62 ismounted in the same longitudinal direction from the vertical centerline70 of the mandrel as establishing means 60 is mounted from the verticalplane 66 through the bending die. Additionally, sensing means 62 ismounted so as to coincide approximately in latitude with theestablishing means 60.

Proper positioning of the mandrel 28 with respect to the bending machine22 is accomplished by causing the movement and the expansion of themandrel 28 to be responsive to the electromagnetic voltage signalsgenerated by the sensing means 62 responsive to the changing magneticfield of the establishing means 60.

When the mandrel 28 has been properly positioned according to thisinvention and the shoes 44 and strips 46 are tightly engaged against theinner surface of the pipe 20, the pipe is firmly and adequatelysupported for bending. Bending may be accomplished through the use ofhydraulic means which forces upward a traversly concave shoe 72 againstthe bottom exterior of the pipe 20 and bends the pipe against thebending die 26. When the desired bend has been imparted to the pipe 20,the arcuate support 24 and bending die 26 are loosened and the hydraulicmeans is retracted, thereby allowing the end of the pipe supported bythe concave shoe 72 to resume a horizontal position. The pipe may thenbe repositioned longitudinally in the pipe bending machine for the nextbend. The mandrel 28 is then repositioned according to this inventionwithin the pipe in order to provide the necessary support at thelocation of the next bend.

DESCRIPTION OF REMOVABLY SECURED GUIDE MEANS FIGS. 1, 2, 3(A) and 3(B)show a practical construction of such a guide means according to thisinvention. The removably secured guide means 58 includes a body 94containing a cylindrical cavity 96 in which a pulley 98 is pivotallymounted by a bolted pin 100. The hose 56 travels through the cavity 96and around the pulley 98.

Connected to the body 94 are three flanges 102, 104 and 106, whichfunction to support removably the guide means 58 to either the wall ofthe pipe or to the mandrel 28. The wall of the pipe is engaged betweenflanges 102 and 104 and an arcuate plate 108 on the rear framework 34 ofthe mandrel 28 is engaged between flanges 104 and 106. The radius ofplate 108 is preferred to be approximately equal to the radius of thepipe 20. Arcuate plate 108 is preferred to be attached to the upperframework 34 in such a location so that when the mandrel 28 moves insidethe pipe 20, the removably secured guide means 58 engages the pipe 20between flanges 102 and 104 and plate 108 is pulled from between flanges104 and 106.

The space between flanges 102 and 104 should be slightly greater thanthe thickness of the wall of the pipe 20 to accommodate the curvature ofpipe 20. Likewise, the thickness of the cavity between the lower twoflanges 104 and 106 should be slightly greater than the thickness of thearcuate plate 108 to accommodate the curvature of plate 108. The ends ofthe flanges are rounded to facilitate entry of the pipe and the arcuateplate into said spaces and to allow for slight misalignment.

The storage wheel 59 functions not only to store the hose 56, but alsoto exert continuously force on the hose in the direction designated bythe arrow 110 in FIG. 1. Since the other end of the hose 56 is attachedto the mandrel 28, there are forces acting continuously on the removablysecured guide means 58in the directions of the arrows 112 and 114 shownin FIG. 3. The spaced relationship of the pipe 20, arcuate plate 108 andflanges 102, 104 and 106 in conjunction with the pressures exerted bythe hose 56, cause the removably secured guide means 58 to be secured tothe arcuate plate 108 of the mandrel whenever the rear of the mandrel isexterior to the pipe 20 and to be secured to the pipe 20 whenever therear of the mandrel is within the pipe 20.

DESCRIPTION OF ESTABLISHING MEANS AND SENSING MEANS FIGS. 1, 6 and 8illustrate a preferred embodiment of the physical construction of thesensing means and establishing mans according to this invention. Thesensing means, broadly designated as 62, is attached to the framework 34of the mandrel 28. Such sensing means 62 is comprised of a ferromagneticcore 118 and an electrical current carrying conductor (not shown) owlcoiled therearound. Such core and conductor are securely molded into orotherwise held by a body 120, preferably non-magnetic, in such a mannerthat the long axis of the U-shaped core is vertically aligned.

The body 120 is pivotally connected to a yoke 122, which in turn ispivotally connected to a plate 124 secured to the framework 34 of themandrel. The body 120 has a bored flange 126 which loosely fits betweentwo bored flanges on the yoke 122. A pin 128 is disposed through the twoflanges on the yoke 122 and the bored flange 126. The diameter of thepin 128 is somewhat less than the diameter of the bore in the flange 126so as to provide a sloppy fit," which aids in the engaging of the body120 against the inner surface of the pipe 20 by allowing for slightmisalignments.

The plate 124 has two bored flanges which fit over the ends of a bore inthe yoke 122. A pin 130 through such flanges pivotally secures the yoketo the plate. The plate is secured to the framework of the mandrel byordinary means such as bolting or welding.

As particularly revealed in FIG. 8, adjustably attached to the body 120are four wheels 132, 134, 136 and 138. Each wheel is pinned between twolugs and the lugs are adjustably attached to the body 120. The fouradjustable wheels function to keep the ends of the core 118 fromscraping the inside of the pipe and, in conjunction with the sloppy fitbetween the body and the yoke, to provide a constant close spacedrelationship between the ends of the core 118 and the inner surface ofthe pipe 20 as the body 120 moves longitudinally along the inside of thepipe.

An actuator means 140 is pivotally connected to the framework 34 and tothe yoke 122 by ordinary means, such as pins and lugs. Such actuatormeans 140, which may be a fluid piston, functions to move plate 120 intoposition with the four wheels in engagement with the inner surface ofthe pipe 20 when expanded and to withdraw the sensing means 62 safelywithin the confines of the framework 34 when retracted. In the preferredembodiment of this invention, such actuator means 140 operates oncompressed air supplied from the hose 56; the flow of the compressed airinto the fluid piston chamber is controlled by a spring-loadedreciprocally moving magnetic device driven by a solenoid pursuant to asupplied electrical signal as hereinafter explained.

Attached to the bending machine exterior to the pipe is the establishingmeans, generally designated by the number 60. Such establishing meansincludes electromagnets 142 and 144, each of which is positioned so thatits positive and negative poles are vertically aligned. Eachelectromagnet 142 and 144 is molded into or attached to a body 146 and148, respectively, which bodies 146 and 148 are pivotally connected toeach other by means such as pin 150 secured in bored flanges attached toeach body. The pivotal connection is provided so that the angle betweenthe surfaces of such bodies may be varied in accordance with the varyingcircumferences of the pipes being bent. The proper angle is maintainedthrough the use of a jackscrew 152 which is attached to the two bodiesby suitable means, such as welded lugs. Body 148 is pivotally connectedby suitable means to a portion of the bending machine 22. The two wheels154 and 156 are adjustably mounted on body 146 as shown. The wheelsfunction to space memo norm the electromagnets 142 and 144 a constantdistance from the exterior surface of the pipe 20 and to allow the pipe20 to move easily with respect to the emitting means 60.

An actuator means 160 pivotally connected to the body 148 and thebending machine function to hold the wheels 154 and 156 firmly againstthe outer surface of the pipe 20 when expanded and to draw theestablishing means 60 back safely away from the pipe when retracted.Such actuator means 160 may be any suitable device, such as a fluidoperated piston similar to that described for the sensing means. Theactuator means 160 is attached to the body 148 and the bending machine22.

ELECTRICAL AND RELATED COMPONENTS FIG. 8 is a block diagram of thepreferred arrangement of the electrical and related components forpositioning a movable pipe supporting mandrel inside a pipe according tothis invention. These components which are preferably located exteriorlyof the pipe are shown within the dashed lines 161. The remainder of thecomponents shown in FIG. 8 are preferably mounted on the mandrel.

Control means 162 functions to transmit energizing signals to theactuator means 160, the driver means 164 for the establishing means 60,and the correlation means 166. Control means 162 is preferably attachedto the pipe bending machine at an easily accessible location.

Pursuant to an energizing signal received from control means 162,actuator means 160 functions as previously described to move and holdthe establishing means 60 in spaced relation to the exterior surface ofthe pipe 20. Pursuant to an energizing signal from the control means162, driver means 164 functions to produce and drive through theelectromagnets in the establishing means 60 an alternating currentsignal of preselected frequency, thereby producing the desired changingmagnetic field.

Switch 168 functions to energize actuator means 140 and amplifying means170. In the preferred embodiment of the invention, switch 168 is a"whisker" switch attached to the rear framework 34 of the mandrel 28 insuch a manner that it is physically turned on when the rear of themandrel enters the pipe and stays on continually while the mandrel isinside the pipe.

Actuator means 140 functions as previously described to move and holdthe sensing means 62 in spaced relation to the inside of the pipe 20.Amplifying means 170 functions to amplify by a preselected gain thevoltage signal generated by the sensing means 62.

Correlation means 166 functions to correlate the signals received fromcontrol means 162 and signals, if any, received from amplifying means170. Control means 162 transmits only two sets of functional signals tothe correlation means 166: enable or disable forward movement of themandrel and enable or disable reverse movement of the mandrel. So longas no signal of preselected desired magnitude is being received fromamplifying means 170, correlation means 166 will function responsive tothe signals received from the control means 162 to energize anddeenergize the forward/reverse actuator means 54 for the prime mover.However. whenever a voltage signal of preselected desired magnitude isreceived from amplifying means 170, the correlation means 166 willde-energize the forward/reverse actuator means 54 and energize theexpansion actuator means 42 for the expansion units 36, 38 and 40(regardless of any signal which might be simultaneously received fromthe control means 162). The correlation means 166 and amplifier means170 are preferably contained in the container 48 attached to theframework 34 of the mandrel 28.

EXTERIOR ELECTRICAL COMPONENTS FIG. 9 is a schematic diagram of apractical arrangement of the electrical components located exteriorly ofthe pipe, that is, control means 162, actuator means 160 and drivermeans 164. The components comprising a preferred control means 162 areshown within the dashed lines.

Onloff switch 172, functions to apply a power voltage source 174, suchas a 12 volt DC battery, across the rest of the circuitry in the controlmeans 162.

One of the functions of the control means 162 is to transmit theoperators signals to the mandrel so that the mandrel can be caused tomove in a forward or reverse direction or to cease movement. This couldwell be accomplished through the use of electrical wires feeding fromthe pipe bending machine to the container 48 on the framework 34 of themandrel. Such wires could be secured to the hose 56 which feeds to themandrel. However, in the preferred embodiment of this invention, suchsignals are transmitted from the control means 162 to the mandrel viaradio waves through the use of transmitting means and receiving means.

Forward transmitting means 176 and reverse transmitting means 178 arestandard devices, each of which functions to generate, pursuant to anenergizing signal, a constant output signal of preselected frequency. lnthe preferred embodiment, for example, forward transmitting means 176generates while energized a UHF signal with a frequency of 275megacycles and reverse transmitting means 178 generates while energizeda UHF signal with a frequency of 285 megacycles.

The operator energizes and de-energizes the forward and reversetransmitting means 176 and 178 through the use of push-button switches180 and 182 respectively, each of which is an ordinary device whichfunctions to pass the DC voltage only while physically depressed. Whenpush-button switch 180 supplies voltage to the input of relay 184, suchrelay functions to close switches 186 and 188 and to open switch 190.The closing of switch 188 applies voltage across and energizes forwardtransmitting means 176. The opening of switch 190 precludes theactivating of relay 192. The reverse push-button switch 182 and itsattendant circuitry functions similarly. It is observed that relay 184and relay 192 are mutually exclusive.

Switch 194 energizes those components utilized to position the mandrellongitudinally inside the pipe. The closing of switch 194 activatesrelay 196, which functions to close switches 198, 200 and 202. Theclosing of switch 198 activates actuator means 160 and driver means 164.Driver means 164 is a standard inverter device which functions totransform the constant DC voltage signal to an AC voltage signal. Forexample, the output of said means 164 may be a 120 volt, 6O cycle persecond, square-wave signal with 500 watts of power. Such signal isdriven through the conductor coiled around the two electromagnets in theestablishing means 60.

The closing of switch 202 creates a potential additional current path torelay 184. Now when relay 184 is activated by push-button switch 180 andswitch 186 closes, relay 184 becomes locked-in due to the currentflowing through such additional current path. Even if the operator is nolonger depressing push-button switch 180, relay 184 and forwardtransmitting means 176 remain activated until switch 194 is opened.Switching means 200 and the circuitry attendant to relay 192 functionssimilarly.

ELECTRICAL COMPONENTS LOCATED ON THE MANDREL FIG. is a schematic diagramof a practical arrangement of the electrical components in thoseportions of the preferred embodiment located on the mandrel. The voltagesource for such electrical components is the DC battery 50 attached tothe framework 34 of the mandrel. On/off switch 202, an ordinary devicemounted on the framework 34 of the mandrel, functions to apply such DCvoltage to and enable all of the electrical components shown in FIG. 10and located on the mandrel except the actuator means 140 for the sensingmeans 62 and amplifying means 170.

As previously stated, in the preferred embodiment of the inventionsignals to control the direction of movement of the mandrel aretransmitted to the mandrel via radio waves. The forward receiving means204 and reverse receiving means 206 are standard devices, each of whichfunctions to receive the radio wave signals generated by the forward andreverse transmitting means 176 and 178, respectively, and to close aswitch 208 and 210, respectively, encompassed therein. The closing ofswitch 208 in forward receiving means 204 provides a current path fromthe output of transistor 212 to the base of transistor 21 4. Likewise,the closing of switch 210 provides a similar current path to the base oftransistor 216. In the normal state of operation, transistor 218 isturned off; transistor 212 is thereby turned on and the voltage fromvoltage source 50 issues from its emitter.

The receipt of the preselected UHF signal by forward receiving means 204closes switch 208 and applies a bias current on the base of transistor214, thereby tuming it on. The current output of transistor 214 turns onpower transistor 220, which produces the driving current necessary toenergize the forward solenoid in the forward/reverse actuator means 54.Similarly, the receipt of the preselected UHF signal by reversereceiving means 206 causes transistor 216 to turn on power transistor222, which generates the driving current necessary to energize thereverse solenoid in the forward/reverse actuator means 54. Transistors214, 216 and 212 are standard devices such as Tl 731. Power transistors218, 220 and 222 are standard devices such as Tl 2N 3054. When nopreselected signal is being received by either receiving means 204 or206, actuator means 54 is not energized and therefore the mandrel doesnot move in either direction.

Diodes 224 and 226 function to protect the rest of the circuitry fromthe effects of the forward and reverse solenoids in the forward/reverseactuator means 54 being de-energized by shorting the large mangitudes ofcurrent and voltage created by the collapsing magnetic fields attendantto the de-energizing of such solenoids.

Switch 168 is the previously discussed whisker switch mounted on theframework 34 at the rear of the mandrel in such a position that itcontacts the wall of the pipe and closes when the rear of the mandrelmoves inside the pipe. Such whisker switch 168 functions to enable theactuator means for the sensing means 62 and the amplifying means onlywhile the mandrel is inside the pipe. This ensures that commonlyoccurring extraneous signals containing sixty cycles per secondfundamental frequency or harmonics thereof do not cause the mandrel toexpand outside the pipe. Once inside the pipe, the sensing means 62 isshielded from such extraneous signals by the pipe itself if the pipe ismade of ferromagnetic material. If, however, the pipe is made ofnon-magnetic material, a power frequency of perhaps 400 cycles persecond may be utilized in the emitter driver means 164 to diminish theeffects of the commonly occurring 60 cycles per second signal;additionally, the gain of the amplifying means 170 and the output of theestablishing means 60 should be adjusted so as to minimize the effect ofsuch extraneous signals.

when actuator means 140 has moved sensing means 62 into its desiredspaced relationship with the inner wall of the pipe and amplifying means170 has been energized, the portions of the preferred apparatus of theinvention located on the mandrel are disposed to position said mandrellongitudinally within the pipe. The voltage signals induced in the coilsof sensing means 62 as a result of the changing magnetic flux sensed bysuch coils are transmitted via a shielded electrical cable 230 throughan R-C circuit to the input of amplifying means 170, a standardoperational amplifier such as a National Semiconductor LM201, whichfunctions to amplify by a preselected gain such voltage signal.

The amplified AC signal, if any, emitted from amplifying means 170 iscoupled to the input of the correlation means 166. Such signal isinitially coupled to transistor 232 which functions as a bufferamplifier to isolate the previous circuitry and present a constantimpedance to the remainder of the circuitry. The AC output of transistor232 is driven through a diode and an R-C circuit which function torectify the AC signal to a DC signal. The rectified DC voltage signal isamplified by transistor 234 and coupled to the base of transistor 236which functions as another buffer amplifier. Transistors 232, 234 and236 are standard devices such as T1 731 transistors.

The amplified voltage signal emitted by transistor 236 turns on powertransistor 218, which generates the driving current necessary toenergize the solenoid in the expansion actuator means 42. When thedriving current is emitted from the collector of transistor 218, thebase of transistor 212 goes to zero voltage and such transistor turnsoff. There is no longer any base current bias on transistors 214 and 216and, accordingly, irrespective of the signals received by receivingmeans 204 and 206, the forward/reverse actuator means 54 cannot beenergized. Diode 238 serves to protect the circuitry from the effects ofthe de-energizing of the solenoid in the expansion actuator means 42.

msmn mm Thus, correlation means 166 functions to obey the commandsignals received from receiving means 204 or 206 only when no signal ofpreselected magnitude is being received from amplifying means 170.However, when a signal of preselected magnitude is received fromamplifying means 170, correlation means 166 deenergizes theforward/reverse actuator means 54 and energizes the expanding actuatormeans 42. The mandrel remains motionless and expanded so long as suchsignal of preselected magnitude is emitted from amplifying means 170.Upon the loss of such signal, correlation means 166 again operatesresponsive to the signals, if any, being received from receiving means204 or 206.

PREFERRED METHOD OF OPERATION FIGS. 1 HA) through 12(G) are a series ofschematic side views of certain parts of a pipe bending machine, a pipesupporting mandrel and a pipe. Such series of views show the steps inthe method of automatically positioning such mandrel longitudinally inthe pipe according to this invention. FIG. 11(A) reveals the mandrel 28resting on its storage pad, which comprises a part of the pipe bendingmachine 22. The hose 56 for transporting compressed air to the mandrelis connected from the storage wheel 59 through the removably securedguide means 58 to the mandrel 28. As previously explained, the removablysecured guide means 58 is attached to the arcuate plate 108 on theframework 34 of the mandrel. A pipe 20 is placed by ordinary meanswithin the confines of the pipe bending machine. The vertical plane 66(represented by a dashed line) through the bending die is the locationin which that portion of the pipe to be bent is to be positioned. Thelocation of the establishing means (not shown) on the pipe bendingmachine is indicated by the vertical dotted line 64 and the intersectinghorizontal dotted line.

The operator energizes the electrical portions of the invention locatedon the mandrel by closing switch 202 (shown in FIG. The electricalportions of the apparatus attached to the pipe bending machine areenergized by closing switch 172 (shown in FIG. 9). The operatordepresses forward push-button switch 180 and the mandrel is movedforward into the pipe.

As the rear framework 34 of the mandrel enters the pipe, whisker switch168 is closed. Sensing means 62 is thereby moved into communication withthe wall of the pipe and amplifying means 170 is enabled. As theremovable secured guide means 58 comes into contact with the wall of thepipe, such means 58 slides off the plate 108 on the framework 34 of themandrel and slides onto the end of the pipe.

Once the mandrel has been moved inside the pipe to a desired approximatelocation, the operator releases forward push-button switch 180 andthereby stops the movement of the mandrel. It is not important how farthe mandrel is moved into the pipe so long as the operator is aware ofwhich side of the plane, represented by the vertical centerline 64 ofestablishing means 60, sensing means 62 is located. FIG. 11(B) shows themandrel stopped just inside the end of the pipe.

The pipe is then positioned by ordinary means so that the portiondesired to be bent is aligned with the vertical plane 66. FIG. 11(C)reveals a situation in which it is desired that the end of the pipefurthest from the mandrel be bent. As the pipe 20 is moved through thepipe bending machine, the mandrel 28 of course moves with it. Therefore,the operator of the pipe bending machine is aware that sensing means 62attached to the mandrel is located with respect to the verticalcenterline 64 of the establishing means such that the mandrel must bemoved in the forward direction to align such sensing and establishingmeans.

Switch 194 (FIG. 9) is closed by the operator, thereby activating drivermeans 164 and actuator means 160. Establishing means 60 is thus placedin a desired close spaced relationship with the exterior surface of thepipe and the changing magnetic field is generated along a vertical planecoincidental with the vertical centerline 64 of the establishing means.The operator depresses forward push-button switch 180, which becomeslocked-in," and the mandrel moves in a forward direction (even if theoperator ceases to depress the forward push-button means) until sensingmeans 62 senses the changing magnetic field emitted by establishingmeans 60 and generates a voltage signal which, when amplified byamplifying means 170, reaches or exceeds the preselected voltagemagnitude necessary to cause correlation means 166 to de-energize theforward solenoid in forward/reverse actuator means 54 and energizeexpansion actuator means 42. Thus the mandrel is properly positioned andexpanded inside the pipe as shown in FIG. 11(D). As shown in FIG. 11(E),the pipe supporting machine bends the pipe by raising the end of thepipe not being held between the shoes of the pipe bending machine.

Generally, however, it is desired that a series of sequential bends beimparted to the pipe. The method and apparatus of positioning themandrel inside the pipe according to this invention allows the automaticpositioning of such mandrel during these sequential bends. The operatordetermines the longitudinal relationship the vertical centerline ofsensing means 62 will have with respect to the vertical centerline 64 ofestablishing means 60 (not shown) as the pipe commences to move to itsnew positions. This determination is made so that the mandrel willtravel in the correct direction. At some point in time prior to movingthe pipe to its new position, the operator correctly adjusts controlmeans 162. As shown in FIG. 11(F), the normal method of sequentiallybending pipe is to retract the bending shoes of the bending machine andmove the pipe approximately 18 inches in the direction designated by thearrow 240. Thus, the operator knows that the mandrel should move in areverse direction to align properly the centerline of sensing means 62with the centerline 64 of establishing means (not shown). Therefore, atsome point in time prior to moving the pipe, the operator opens switch194 and thereby unlocks" forward relay 184. The operator then againcloses switch 194 and depresses the reverse push-button switch 182(reverse relay 192 then becomes "locked-in").

As the pipe is moved in the direction designated by arrow 240, themandrel and its attendant sensing means 62 are also moved in suchdirection. As soon as sensing means 62 moves from within the changingmagnetic field generated by establishing means 60 sufficiently todecrease its amplified voltage signal below the preselected magnitude,correlation means 166 de-energizes the expansion actuator means 42 and,pursuant to the signal being received continuously from reversereceiving means 206, energizes the reverse solenoid in forward/reverseactuator means 54 and moves the mandrel in the reverse direction. FIG.11(F) shows in exaggeration the relative position of sensing means 62 onthe mandrel with respect to the centerline 64 of establishing means 60(not shown) as the pipe is moved in the direction denoted by the arrow240 in preparation for the next bend. The mandrel moves in the reversedirection until the voltage induced in the sensing means 62, asamplified by amplifier 170 and acted upon by the correlation means 166,causes the mandrel to stop and to expand at the proper longitudinalposition, FIG. 12(6). Throughout the series of sequential moves of thepipe in the direction denoted by the arrow 240, the method and apparatusaccording to this invention automatically positions the mandrel withoutany additional commands or instructions being transmitted by theoperator. The automatic operation of the mandrel is, of course, notlimited to movement of the mandrel in the direction denoted by arrow240. Rather, the circuitry controlling the automatic operation of themandrel can be employed to move the mandrel automatically in one ofeither the forward or reverse directions.

The invention has been shown and defined with reference to a particularembodiment. However, many variations and modifications of the inventionwill now be apparent to those having skill in the art. For instance, theinvention is not limited to use with a tubular structure, but may beused to position elements on opposite sides of a partition. Additionallythe circuitry and physical components included in the invention may bearranged and constructed in a myriad of different forms. Therefore, itis felt that the foregoing disclosure and description of the inventionare only illustrative and explanatory, and various changes in thecircuitry and components, as well as in the details of the illustratedconstruction, may be made within the scope of the appended claimswithout departing from the spirit of the invention.

What is claimed is:

1. A method of positioning a movable mandrel longitudinally along theinterior of a pipe at a desired location with respect to an elementlocated exteriorly of said pipe, including the steps of establishing aperiodically changing magnetic field at a desired location at one of theexterior of said pipe and the interior of said pipe, the meansestablishing said changing magnetic field being mounted in a desiredfixed relationship to one of the said element and the said mandrel,respectively, and being located in a sufiiciently close spacedrelationship with the wall of said pipe so that said wall is within saidchanging magnetic field,

sensing said changing magnetic field at the other of the exterior ofsaid pipe and the interior of said pipe and generating anelectromagnetic voltage signal responsive thereto, said means forsensing and generating being mounted in a desired fixed relationship tothe second of said element and said mandrel, and

moving said mandrel and the one of said establishing means and saidsensing and generating means mounted in fixed relationship theretolongitudinally along the interior of said pipe to position saidestablishing means and said sensing and generating means in a desiredrelationship to each other, said mandrel and said element thereby beingpositioned in a desired relationship to each other.

2. A method according to claim 1, wherein said step of establishing achanging magnetic field at a desired location includes driving analternating current electrical signal of preselected frequency through acurrent carrying conductor coiled around a ferromagnetic core.

3. A method according to claim 1, including the step of performing adesired function responsive to a desired magnitude of said generatedelectromagnetic voltage signal. 4. A method according to claim 3,wherein said step of performing a desired function includes stoppingsaid movement of said mandrel so that said establishing means and saidsensing and generating means are positioned in a desired relationship toeach other and said mandrel and said element are likewise positioned ina desired relationship to each other. 5. A method according to claim 1,including the steps of stopping said mandrel responsive to a desiredmagnitude of said generated electromagnetic voltage signal so that saidestablishing means and said sensing and generating means are positionedin a desired close spaced relationship to each other and said mandrel islikewise positioned in a desired location with respect to said element,and

performing an additional desired function responsive to a desiredmagnitude of said generated electromagnetic voltage signal.

6. A method of automatically positioning a movable pipe supportingmandrel at a series of locations longitudinally along the interior of apipe positioned in a pipe bending machine during the pipe bendingprocess, including the steps of a. positioning said pipe with saidmandrel therein in a first desired location in said pipe bending machineso that said pipe is in the proper location for the first bend,

. establishing a periodically changing magnetic field in a desiredlocation exteriorly of said pipe, the means establishing such changingmagnetic field being mounted in a desired fixed relationship to saidpipe bending machine and being located in a sufficiently close spacedrelationship with the wall of said pipe that said wall is within saidchanging magnetic field,

c. moving said mandrel in a first direction so that said sensing andgenerating means moves toward said establishing means to position saidestablishing means and said sensing and generating means in a desiredrelationship to each other,

. sensing said changing magnetic field at the interior of said pipe andgenerating an electromagnetic voltage signal responsive thereto, themeans for sensing and generating being mounted in a desired fixedrelationship to said mandrel, the desired stopping said mandrelresponsive to a desired magnitude of said generated electromagneticvoltage signal so that said establishing means and said sensing andgenerating means are positioned in a desired close spaced relationshipto each other and said mandrel is positioned in a desired relationshipto said pipe bending machine, and

. actuating said mandrel responsive to a desired magnitude of saidgenerated electromagnetic voltage signal to support the interior of saidwall of said pipe during the first bend in the pipe bending process.

7. A method according to claim 6, including the steps g. bending saidpipe, h. moving said pipe with said mandrel therein to a second desiredlocation in said pipe bending machine so that said pipe is in the properlocation for the second bend,

i. deactuating said mandrel responsive to the reducrepeating tion ofsaid generated electromagnetic voltage signal below said desiredmagnitude so that said mandrel no longer is supporting said interior ofsaid wall of said pipe,

. moving said mandrel in the one of the first and second directions sothat said sensing and generating means moves toward said establishingmeans to reposition said sensing and generating means and saidestablishing means in a desired relationship to each other, and

the above steps d,e,f,g,h,i, and j, throughout the pipe bending process.

8. A method according to claim 6, wherein said step of establishing achanging magnetic field at a desired location exteriorly to the pipeincludes driving an alternating current electrical signal of preselectedfrequency through a current carrying conductor coiled around aferromagnetic core.

9. An apparatus for positioning a movable mandrel longitudinally alongthe interior of a pipe at a desired location with respect to an elementlocated exteriorly of said pipe, comprising means for establishing aperiodically changing magnetic field at a desired location at one of theexterior of said pipe and the interior of said pipe, said establishingmeans being mounted in a desired fixed relationship to one of the saidelement and the said mandrel, respectively, and being located in asufficiently close spaced relationship with the wall of said pipe sothat said wall is within said changing magnetic field,

means for sensing said changing magnetic field at the other of theexterior of said pipe and the interior of said pipe and generating anelectromagnetic voltage signal responsive thereto, said sensing andgenerating means being mounted in a desired fixed relationship to thesecond of said element and said mandrel, respectively, and

means for moving said mandrel and the one of said establishing means andsaid sensing and generating means mounted in fixed relationship theretolongitudinally along the interior of said pipe so that said establishingmeans and said sensing and generating means are positioned in a desiredrelationship to each other and said mandrel and said element are therebypositioned in a desired relationship to each other.

10. An apparatus according to claim 9, wherein said means forestablishing said changing magnetic field includes a ferromagnetic core,

means for conducting electrical current coiled around said ferromagneticcore, and

means for driving an alternating current electrical signal ofpreselected frequency through said conductor means.

1 1. An apparatus according to claim 9, including means for performing adesired function responsive to a desired magnitude of said generatedelectromagnetic voltage signal.

12. An apparatus according to claim 9, including means for stopping saidmovement of said mandrel so that said establishing means and saidsensing and generating means are positioned in a desired relationship toeach other and said mandrel and said element are thereby positioned in adesired relationship to each other, and

means for performing a desired function responsive to a desiredmagnitude of said generated electromagnetic voltage signal.

13. An apparatus for automatically positioning a movable pipe supportingmandrel at a series of locations longitudinally along the interior of apipe held in a pipe bending machine during the pipe bending process,comprising a pipe supporting mandrel,

means for establishing a periodically changing magnetic field at adesired location at the exterior of said pipe,

means for holding said establishing means in a close spaced relationshipwith the exterior surface of said wall of said pipe so that said wallwill be within said changing magnetic field, said holding means beingmounted in a desired fixed relationship to said pipe bending machine,

means for moving said mandrel in one of a first and second longitudinaldirections within the pipe, means on said mandrel for supporting theinterior of said pipe during the bending of said pipe, means for sensingat the interior of said pipe said changing magnetic field and generatingan electromagnetic voltage signal responsive thereto,

means for holding said sensing means in a desired spaced relationshipwith the interior of the wall of said pipe, said holding means for saidsensing means being mounted in a desired fixed relationship to saidmandrel, and

means for disengaging said moving means and for engaging said supportingmeans responsive to a desired magnitude of said generatedelectromagnetic voltage signal.

14. An apparatus according to claim 22, wherein said means for holdingsaid sensing means in a desired relationship with the interior of thewall of said pipe includes means for mounting said sensing means, saidmounting means being movably secured to said mandrel, at least oneadjustably positioned wheel secured to said mounting means, and

means for retaining said wheel in contact with the interior of the wallof said pipe.

15. An apparatus according to claim 13, wherein said means for holdingsaid establishing means in close spaced relationship with the exteriorof the wall of said pipe includes means for mounting said establishingmeans,

said mounting means being movably secured to an element exterior to saidpipe,

at least one adjustably positioned wheel secured to said mounting means,and

means for retaining said wheel against the exterior of the wall of saidpipe.

16. An apparatus according to claim 13, wherein said establishing meansincludes a ferromagnetic core,

means for conducting electrical current coiled around said ferromagneticcore, and

means for driving an alternating current electrical signal ofpreselected frequency through said conductor means.

17. An apparatus according to claim 13, wherein said sensing meansincludes a ferromagnetic core, and

means for conducting electrical current coiled around said ferromagneticcore.

18. An apparatus according to claim 13, wherein said moving means forsaid mandrel includes a fluid driven prime mover,

means for supplying fluid to said fluid driven prime mover, and

means for controlling the flow of said fluid to said fluid driven primemover to drive said prime mover in one of the first and seconddirections and to stop said prime mover.

19. An apparatus according to claim 18, wherein said means for supplyingfluid to said prime mover includes a spring loaded revolving storagewheel located exteriorly of said pipe,

a hose for transporting said fluid, and

means for guiding said hose from said storage wheel to said mandrel,said guide means being adapted to be supported on said mandrel when saidmandrel is outside said pipe and supported on the end of said pipe whensaid mandrel is within said pipe, said hose extending from said storagewheel through said removably secured guide means to said means forcontrolling the flow to said fluid driven prime mover.

20. An apparatus according to claim 19, wherein said removably securedguide means includes a body having at one end two parallel flanges witha cavity there-between,

a pulley secured in said cavity between said flanges so that it mayfreely rotate about its axis,

three parallel flanges formed at the other end of said body, said threeflanges being fonned in parallel a f i u er and lowe cav't'e d sai itiiii ri'afig in g spaced so that the wa of said pipe may be received insaid upper cavity and said arcuate plate may be received in said lowercavity for supporting said guide means.

i i i t mmm non

1. A method of positioning a movable mandrel longitudinally along theinterior of a pipe at a desired location with respect to an elementlocated exteriorly of said pipe, including the steps of establishing aperiodically changing magnetic field at a desired location at one of theexterior of said pipe and the interior of said pipe, the meansestablishing said changing magnetic field being mounted in a desiredfixed relationship to one of the said element and the said mandrel,respectively, and being located in a sufficiently close spacedrelationship with the wall of said pipe so that said wall is within saidchanging magnetic field, sensing said changing magnetic field at theother of the exterior of said pipe and the interior of said pipe andgenerating an electromagnetic voltage signal responsive thereto, saidmeans for sensing and generating being mounted in a desired fixedrelationship to the second of said element and said mandrel, and movingsaid mandrel and the one of said establishing means and said sensing andgenerating means mounted in fixed relationship thereto longitudinallyalong the interior of said pipe to position said establishing means andsaid sensing and generating means in a desired relationship to eachother, said mandrel and said element thereby being positioned in adesired relationship to each other.
 2. A method according to claim 1,wherein said step of establishing a changing magnetic field at a desiredlocation includes driving an alternating current electrical signal ofpreselected frequency through a current carrying conductor coiled arounda ferromagnetic core.
 3. A method according to claim 1, including thestep of performing a desired function responsive to a desired magnitudeof said generated electromagnetic voltage signal.
 4. A method accordingto claim 3, wherein said step of performing a desired function includesstopping said movement of said mandrel so that said establishing meansand said sensing and generating means are positioned in a desiredrelationship to each other and said mandrel and said element arelikewise positioned in a desired relationship to each other.
 5. A methodaccording to claim 1, including the steps of stopping said mandrelresponsive to a desired magnitude of said generated electromagneticvoltage signal so that said establishing means and said sensing andgenerating means are positioned in a desired close spaced relationshipto each other and said mandrel is likewise positioned in a desiredlocation with respect to said element, and performing an additionaldesired function responsive to a desired magnitude of said generatedelectromagnetic voltage signal.
 6. A method of automatically positioninga movable pipe supporting mandrel at a series of locationslongitudinally along the interior of a pipe positioned in a pipe bendingmachine during the pipe bending process, including the steps of a.positioning said pipe with said mandrel therein in a first desiredlocation in said pipe bending machine so that said pipe is in the properlocation for the first bend, b. establishing a periodically changingmagnetic field in a desired location exteriorly of said pipe, the meansestablishing such changing magnetic field being mounted in a desiredfixed relationship to said pipe bending machine and being located in asufficiently close spaced relationship with the wall of said pipe thatsaid wall is within said changing magnetic field, c. moving said mandrelin a first direction so that said sensing and generating means movestoward said establishing means to position said establishing means andsaid sensing and generating means in a desired relationship to eachother, d. sensing said changing magnetic field at the interior of saidpipe and generating an electromagnetic voltage signal responsivethereto, the means for sensing and generating being mounted in a desiredfixed relationship to said mandrel, the desired fixed relationship ofsaid establishing mean with said pipe bending machine and the desiredfixed relationship of said sensing and generating means with saidmandrel being such that when said establishing means and said sensingand generating means are in a desired relationship to each other, saidmandrel and said pipe bending machine are in a desired relationship toeach other, e. stopping said mandrel responsive to a desired magnitudeof said generated electromagnetic voltage signal so that saidestablishing means and said sensing and generating means are positionedin a desired close spaced relationship to each other and said mandrel ispositioned in a desired relationship to said pipe bending machine, andf. actuating said mandrel responsive to a desired magnitude of saidgenerated electromagnetic voltage signal to support the interior of saidwall of said pipe during the first bend in the pipe bending process. 7.A method according to claim 6, including the steps of g. bending saidpipe, h. moving said pipe with said mandrel therein to a second desiredlocation in said pipe bending machine so that said pipe is in the properlocation for the second bend, i. deactuating said mandrel responsive tothe reduction of said generated electromagnetic voltage signal belowsaid desired magnitude so that said mandrel no longer is supporting saidinterior of said wall of said pipe, j. moving said mandrel in the one ofthe first and second directions so that said sensing and generatingmeans moves toward said establishing means to reposition said sensingand generating means and said establishing means in a desiredrelationship to each other, and repeating the above steps d,e,f,g,h,i,and j, throughout the pipe bending process.
 8. A method according toclaim 6, wherein said step of establishing a changing magnetic field ata desired location exteriorly to the pipe includes driving analternating current electrical signal of preselected frequency through acurrent carrying conductor coiled around a ferromagnetic core.
 9. Anapparatus for positioning a movable mandrel longitudinally along theinterior of a pipe at a desired location with respect to an elementlocated exteriorly of said pipe, comprising means for establishing aperiodically changing magnetic field at a desired location at one of theexterior of said pipe and the interior of said pipe, said establishingmeans being mounted in a desired fixed relationship to one of the saidelement and the said mandrel, respectively, and being located in asufficiently close spaced relationship with the wall of said pipe sothat said wall is within said changing magnetic field, means for sensingsaid changing magnetic field at the other of the exterior of said pipeand the interior of said pipe and generating an electromagnetic voltagesignal responsive thereto, said sensing and generating means beingmounted in a desired fixed relationship to the second of said elementand said mandrel, respectively, and means for moving said mandrel andthe one of said establishing means and said sensing and generating meansmounted in fixed relationship thereto longitudinally along the interiorof said pipe so that said establishing means and said sensing andgenerating means are positioned in a desired relationship to each otherand said mandrel and said element are thereby positioned in a desiredrelationship to each other.
 10. An apparatus according to claim 9,wherein said means for establishing said changing magnetic fieldincludes a ferromagnetic core, means for conducting electrical currentcoiled around said ferromagnetic core, and means for driving analternating current electrical signal of preselected frequency throughsaid conductor means.
 11. An apparatus according to claim 9, includingmeans for performing a desired function responsive to a desiredmagnitude of said generated electromagnetic voltage signal.
 12. Anapparatus according to claim 9, including means for stopping saidmovement of said mandrel so that said establishing means and saidsensing and generating means are positioned in a desired relationship toeach other and said mandrel and said element are thereby positioned in adesired relationship to each other, and means for performing a desiredfunction responsive to a desired magnitude of said generatedelectromagnetic voltage signal.
 13. An apparatus for automaticallypositioning a movable pipe supporting mandrel at a series of locationslongitudinally along the interior of a pipe held in a pipe bendingmachine during the pipe bending process, comprising a pipe supportingmandrel, means for establishing a periodically changing magnetic fieldat a desired location at the exterior of said pipe, means for holdingsaid establishing means in a close spaced relationship with the exteriorsurface of said wall of said pipe so that said wall will be within saidchanging magnetic field, said holding means being mounted in a desiredfixed relationship to said pipe bending machine, means for moving saidmandrel in one of a first and second longitudinal directions within thepipe, means on said mandrel for supporting the interior of said pipeduring the bending of said pipe, means for sensing at the interior ofsaid pipe said changing magnetic field and generating an electromagneticvoltage signal responsive thereto, means for holding said sensing meansin a desired spaced relationship with the interior of the wall of saidpipe, said holding means for said sensing means being mounted in adesired fixed relationship to said mandrel, and means for disengagingsaid moving means and for engaging said supporting means responsive to adesired magnitude of said generated electromagnetic voltage signal. 14.An apparatus according to claim 22, wherein saId means for holding saidsensing means in a desired relationship with the interior of the wall ofsaid pipe includes means for mounting said sensing means, said mountingmeans being movably secured to said mandrel, at least one adjustablypositioned wheel secured to said mounting means, and means for retainingsaid wheel in contact with the interior of the wall of said pipe.
 15. Anapparatus according to claim 13, wherein said means for holding saidestablishing means in close spaced relationship with the exterior of thewall of said pipe includes means for mounting said establishing means,said mounting means being movably secured to an element exterior to saidpipe, at least one adjustably positioned wheel secured to said mountingmeans, and means for retaining said wheel against the exterior of thewall of said pipe.
 16. An apparatus according to claim 13, wherein saidestablishing means includes a ferromagnetic core, means for conductingelectrical current coiled around said ferromagnetic core, and means fordriving an alternating current electrical signal of preselectedfrequency through said conductor means.
 17. An apparatus according toclaim 13, wherein said sensing means includes a ferromagnetic core, andmeans for conducting electrical current coiled around said ferromagneticcore.
 18. An apparatus according to claim 13, wherein said moving meansfor said mandrel includes a fluid driven prime mover, means forsupplying fluid to said fluid driven prime mover, and means forcontrolling the flow of said fluid to said fluid driven prime mover todrive said prime mover in one of the first and second directions and tostop said prime mover.
 19. An apparatus according to claim 18, whereinsaid means for supplying fluid to said prime mover includes a springloaded revolving storage wheel located exteriorly of said pipe, a hosefor transporting said fluid, and means for guiding said hose from saidstorage wheel to said mandrel, said guide means being adapted to besupported on said mandrel when said mandrel is outside said pipe andsupported on the end of said pipe when said mandrel is within said pipe,said hose extending from said storage wheel through said removablysecured guide means to said means for controlling the flow to said fluiddriven prime mover.
 20. An apparatus according to claim 19, wherein saidremovably secured guide means includes a body having at one end twoparallel flanges with a cavity there-between, a pulley secured in saidcavity between said flanges so that it may freely rotate about its axis,three parallel flanges formed at the other end of said body, said threeflanges being formed in parallel planes and forming upper and lowercavities, and said three flanges being spaced so that the wall of saidpipe may be received in said upper cavity and said arcuate plate may bereceived in said lower cavity for supporting said guide means.